Direct current magnetohydrodynamic pump

ABSTRACT

The invention is for an apparatus and method for pumping of electrically conductive liquids such as liquid metals and electrolytes. The apparatus of the present invention is a self-contained direct current (DC) magneto-hydrodynamic (MHD) pump assembly formed by an upper core assembly, lower core assembly, and a flow channel. The flow channel is formed when the upper core assembly and the lower core assembly are put together. Permanent magnets are used to produce magnetic field inside the flow channel. When the flow channel is filled with electrically conductive liquid, the liquid comes into contact with electrodes within the lower core assembly. The electrodes may be used to draw electric current through the liquid, thereby generating MHD force onto it. As a result, a pressure may be generated within the liquid and/or the liquid may be caused to flow.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority from U.S. provisional patent applications U.S. Ser. No. 61/849,723, filed on Feb. 2, 2013 and entitled “THERMAL MANAGEMENT FOR SOLID STATE HIGH-POWER ELECTRONICS,” and U.S. Ser. No. 61/855,824, filed on May 25, 2013 and entitled “MAGNETOHYDRODYNAMIC ACTUATOR,” the entire contents of all of which are hereby expressly incorporated by reference. This patent application is a continuation-in-part patent application of: U.S. Ser. No. 13/986,084 filed on Mar. 30, 2013 and entitled THERMAL MANAGEMENT DEVICE FOR HIGH-HEAT FLUX ELECTRONICS; the entire contents of which are hereby expressly incorporated by reference.

GOVERNMENT RIGHTS NOTICE

This invention was made with Government support under Contract No. FA9453-10-C-0061 awarded by the U.S. Air Force. The Government has certain rights in the invention.

FIELD OF THE INVENTION

This invention relates generally to a magnetohydrodynamic (MHD) pump and more specifically to a direct current MHD pump.

BACKGROUND OF THE INVENTION

The subject invention is an apparatus and a method for pumping electrically conductive liquids.

Many liquids are electrically conductive. A variety of electrically conductive liquids, such as certain liquid metals and certain aqueous electrolytes may be pumped to achieve specific desired outcome such as thermal management or actuation of components.

It is well known in the art that electrically conductive liquids may be pumped by magnetohydrodynamic (MHD) effect. Pumps operating in accordance with the MHD effect are known as MHD pumps. One advantage of MHD pumps is that they may not require any moving components. MHD pumps can be generally classified according to the nature of the electric current used for their operation as 1) direct current (DC) MHD pumps and 2) alternating current (AC) MHD pumps. DC MHD pumps may have substantially lower power consumption because permanent magnets may be used to generate the required magnetic field.

Prior art MHD pumps show significant complexity, which makes it challenging to scale them down in size to meet the compactness criteria required by many applications. Other challenges include corrosiveness of many liquid metals and electrolytes. MHD pumps are also susceptible to deleterious MHD effects such a Hartman layers, which reduce effectiveness. In addition, magnetic field produced permanent magnets in a gap of a given size is known to fall of as the magnet size is reduce, thus limiting the MHD pump performance. The static pressure “p” producible by an MHD pump may be theoretically expressed as p=B.I/h, where “B” is magnetic flux density (measured, e.g., in Tesla), “I” is electric current (measured, e.g., in Amperes), and “h” is the vertical height of the flow channel inside the MHD pump (measured, e.g., in meters). This formula offers the designer a variety of trades between p, B, I, and h. For example, to produce a target pressure value “p”, one may select a large value of magnetic flux density “B” (which may be produced by permanent magnet with no energy added) to conserve electric current “I” while maintaining the channel height “h” within practical range.

In summary, prior art does not teach an MHD pump capable of producing high pressure at high flow rate that is also efficient, compact, simple, and easy to produce. It is against this background that the significant improvements and advancements of the present invention have taken place.

SUMMARY OF THE INVENTION

The present invention provides an MHD pump assembly for pumping of electrically conductive liquids.

In one preferred embodiment of the present invention, the MHD pump assembly comprises an upper core assembly, a lower core assembly, and a flow channel. The flow channel is formed by the upper core assembly and a lower core assembly when the two assemblies are put together. In particular, the upper core assembly and the lower core assembly are held together only by magnetic forces provided by permanent magnets within. The upper core assembly comprises a core structure, permanent magnet, and electrically insulating material. The lower core assembly comprises a core structure, permanent magnet, a pair of electrodes, and electrically insulating material. When the MHD pump assembly is formed, the core structures provide a low reluctance path for magnetic flux emanating from the permanent magnets to form a magnetic circuit, which passes through the flow channel. As a result, a very high magnetic flux density can be generated in the MHD pump flow channel between the electrodes. In addition, the core structures provide magnetic shielding to surrounding components. The permanent magnets are substantially wider than the electrodes to provide a substantially uniform magnetic flux density in the portion of the flow channel between the electrodes. This feature may allow the MHD pump assembly to operate at high efficiency.

Accordingly, it is an object of the present invention to provide an MHD pump assembly for pumping of electrically conductive liquid. The MHD pump is capable of producing high pressure at high flow rate, while also being efficient, compact, simple, and suitable for large volume production.

It is another object of the invention to provide means for pumping electrically conductive liquids.

It is still another object of the invention to provide an MHD pump having very low stray magnetic field outside the pump volume.

It is an additional object of the invention to provide an MHD pump robust to corrosion by gallium-based liquid metals.

It is yet another object of the invention to provide an MHD pump with self-sealing capability.

These and other objects of the present invention will become apparent upon a reading of the following specification and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an isometric view of the MHD pump in accordance with one embodiment of the invention.

FIG. 2 is a cross-sectional view 2-2 of the MHD pump shown in FIG. 1.

FIG. 3 is an isometric view of the upper core assembly.

FIG. 4 is cross-sectional view 4-4 of the upper core assembly of FIG. 3.

FIG. 5 is an isometric view of the upper core structure.

FIG. 6 is an isometric view of the lower core assembly.

FIG. 7 is a cross-sectional view 7-7 of the lower core assembly of FIG. 6.

FIG. 8 is an isometric view of the lower core structure.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Selected embodiments of the present invention will now be explained with reference to drawings. In the drawings, identical components are provided with identical reference symbols in one or more of the figures. It will be apparent to those skilled in the art from this disclosure that the following descriptions of the embodiments of the present invention are merely exemplary in nature and are in no way intended to limit the invention, its application, or uses.

Referring now to FIG. 1, there is shown an isometric view of the MHD pump assembly 10 in accordance with one embodiment of the subject invention generally comprising an upper core assembly 180, a lower core assembly 182, and a flow channel 104.

The flow channel 104 is formed by the upper core assembly 180 and the lower core assembly 182 when the two assemblies are put together. FIG. 2 shows a cross-sectional view 2-2 of the MHD pump assembly shown in FIG. 1 while exposing additional elements. The upper core assembly 180 is shown (flipped over) in FIG. 3. FIG. 4 is a cross-sectional view 4-4 of the upper core assembly of FIG. 3 showing an upper core structure 186 equipped with a magnet 128 a, electrically insulating filler material 192 a, and an electrically insulating film 198 a. The upper core structure 186 (shown as a stand-alone component in FIG. 5) is formed from a suitable ferromagnetic material capable of carrying magnetic flux at high flux density such as iron, steel, low carbon steel, core iron (e.g., Consumet® by Cartpenter Steel), substantially pure iron, nickel-iron alloys such as Hiperco®, or alike. The electrically insulating filler material 192 a may be epoxy, plastic (e.g., Ultem®), ceramic potting compound, or other suitable material having good electrical insulating properties. The electrically insulating film 198 a may be a suitable film formed from plastic (e.g., Mylar® or Kapton®), epoxy, epoxy paint or other material having good electrical insulating properties. The magnet 128 a is a suitable permanent magnet magnetized through its large faces in a direction parallel to the broken line 181 a. The magnet 128 a may be bonded to the upper core structure 186.

The lower core assembly 182 is shown in FIG. 6. FIG. 7 is a cross-sectional view 7-7 of the lower core assembly of FIG. 6 showing a lower core structure 190 equipped with a magnet 128 b, electrically insulating filler material 192 b, electrodes 130 a and 130 b, and an electrically insulating film 198 b. The lower core structure 190 (shown as a stand-alone component in FIG. 8) is formed from a suitable ferromagnetic material capable of carrying magnetic flux at high density such as iron, steel, low carbon steel, core iron (e.g., Consumet® by Cartpenter Steel), pure iron, nickel-iron alloys such as Hiperco®, or alike. The electrically insulating filler material 192 b may be epoxy, or plastic (e.g., Ultem), ceramic potting compound, or other suitable material having good electrical insulating properties. The electrically insulating film 198 b may be a suitable film formed from plastic (e.g., Mylar® or Kapton®), epoxy, epoxy paint, or other material having good electrical insulating properties.

The lower core assembly 182 has a groove 188 designed to form a portion of the flow channel 104 when the MHD pump assembly 10 is formed. The groove 188 is formed by selected surfaces of the lower core structure 190, electrically insulating filler material 192 b, electrodes 130 a and 130 b, and the electrically insulating film 198 b. The groove 188 has a width “W” and a height “H” (FIG. 1). The width “W” and the height “H” may not have to be constant within the lower core assembly 182. For example, the width “W” may be reduced between the electrodes 130 a and 130 b. Because the flow channel 104 is formed when the upper core assembly 180 and the lower core assembly 182 are put together, the width “W” and the height “H” of the flow channel 104 may be substantially same as those of the groove 188. The magnet 128 b is a suitable permanent magnet magnetized through its large faces in a direction parallel to the broken line 181 b. The magnet 128 b may be bonded to the upper core structure 190.

The magnets 128 a and 128 b (see, e.g., FIGS. 2, 4 and 7) are suitable permanent magnets magnetized through their large faces in a direction parallel to the arrows 181 a and 181 b, respectively. The magnets 128 a and 128 b are preferably rare earth permanent magnets formed from samarium-cobalt (SmCo) or from neodymium-iron-boron (NdFeB) materials. The magnetization of the magnets 128 a and 128 b should be arranged so that their magnetization vectors are substantially pointing in the same direction when the MHD pump assembly 10 (FIG. 1) is formed. Because of the magnetization vector alignment, the upper core assembly 180 and the lower core assembly 182 attract each other. As a result, the MHD pump assembly 10 may be formed without any fasteners, thus allowing for simple construction and installation.

The electrodes 130 a and 130 b are preferably made of tungsten, tantalum, or other suitable material having high electrical conductivity as well as robustness to erosion by electrical arc. Alternatively, the electrodes may be made of copper or copper alloy and they may be plated with a suitable refractory metal such as, but not limited to molybdenum, tungsten, tantalum, ruthenium, osmium, and iridium. The edge 152 of the electrodes facing the flow channel 104 may be curved (as shown in FIG. 6) or it may be straight. Curved edge may make the electrode less susceptible to electrical arcing.

The electrodes 130 a and 130 b, the insulating filler materials 192 a and 192 b, and the insulating films 198 a and 198 b are preferably installed to prevent electrical contact between the electrodes and the upper core structure 196, the lower core structure 190, the magnet 128 a, and the magnet 128 b.

Preferably, the mating surfaces of the upper core assembly 180 and the lower core assembly 182 are fabricated so that upon forming the MHD pump assembly 10 with no additional seals are required. Alternatively, when the MHD pump assembly 10 is formed, a suitable adhesive or sealant (e.g., epoxy or cyanoacrylate adhesive) may be applied to the joints to seal the flow channel 104 and to prevent potential leakage of conductive liquid from the pump.

It is important that all surfaces of AHS 10 that may come into contact with the liquid being pumped (such as liquid metal, electrolyte, or alike) be made of compatible materials. In particular, it is well know that liquid gallium and its alloys severely corrode many metals. Literature indicates that certain refractory metals such as tantalum, tungsten, and ruthenium may be stable in gallium and its alloys. See, for example, “Effects of Gallium on Materials at Elevated Temperatures,” by W.D. Wilkinson, Argonne National Laboratory Report ANL-5027, published by the U.S. Atomic Energy Commission (Aug. 1953). To protect against corrosion, vulnerable surfaces that may come into contact with the liquid metal coolant (for example portions of the body 102) may be coated with suitable protective film. Suitable protective coatings and films for copper parts (e.g., the body 102) may include sulfamate (electroless) nickel, electroplated ruthenium, titanium nitride (TiN), and diamond-like coating (DLC). Diamond-like coating may be obtained from Richter Precision in East Petersburg, Pa. The Applicant has determined that core structures 186 and 190 made of substantially pure iron or core iron (e.g., Consumet® by Cartpenter Steel) may not require a protective coating. Reduced need for protective coatings simplifies fabrication and reduces cost.

In operation, the flow channel 104 of the MHD pump assembly 10 may be substantially filled with suitable electrically conductive liquid. The electrodes 130 a and 130 b may be electrically connected to the terminals of a source of direct electric current, such a battery or a power supply. For example, the electrode 130 a may be electrically connected to a negative terminal (or the ground terminal) of the source of direct electric current, and the electrode 130 b may be electrically connected to a positive terminal of the source of direct electric current. The liquid inside the flow channel 104 makes an electrical contact with the electrodes 130 a and 130 b and allows an electric current to flow from one electrode to another electrode. In particular, the current flows through the liquid metal located generally between the electrodes. Because the portion of the flow channel 104 between the electrodes is immersed in a magnetic field generated by the permanent magnets 128 a and 128 b, drawing of electric current though the liquid therein generates a force on the liquid. Such a force may be directed so as to flow the liquid inside the flow channel 104 or generate a pressure within. The direction of the electric current (as defined by the polarity of the electric current source) drawn though the liquid may be coordinated with the direction of the magnetic field generated by the magnets 128 a and 128 b to define the direction of liquid flow.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” and “includes” and/or “including” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

The terms of degree such as “substantially”, “about” and “approximately” as used herein mean a reasonable amount of deviation of the modified term such that the end result is not significantly changed. For example, these terms can be construed as including a deviation of at least ±5% of the modified term if this deviation would not negate the meaning of the word it modifies.

The term “suitable,” as used herein, means having characteristics that are sufficient to produce a desired result. Suitability for the intended purpose can be determined by one of ordinary skill in the art using only routine experimentation.

Moreover, terms that are expressed as “means-plus function” in the claims should include any structure that can be utilized to carry out the function of that part of the present invention. In addition, the term “configured” as used herein to describe a component, section or part of a device includes hardware and/or software that is constructed and/or programmed to carry out the desired function.

Different aspects of the invention may be combined in any suitable way.

While only selected embodiments have been chosen to illustrate the present invention, it will be apparent to those skilled in the art from this disclosure that various changes and modifications can be made herein without departing from the scope of the present invention as defined in the appended claims. Furthermore, the foregoing description of the embodiments according to the present invention are provided for illustration only, and not for the purpose of limiting the present invention as defined by the appended claims and their equivalents. Thus, the scope of the present invention is not limited to the disclosed embodiments. 

What is claimed is:
 1. A magnetohydrodynamic (MHD) pump assembly comprising an upper core assembly, a lower core assembly, and a flow channel; a) said flow channel being formed entirely by said upper core assembly and said lower core assembly; b) said upper core assembly comprising an upper core structure, permanent magnet, and electrically insulating material; c) said lower core assembly comprising a lower core structure, permanent magnet, two electrodes, and electrically insulating material; and d) said lower core assembly further comprising a groove forming in-part said flow channel.
 2. The MHD pump assembly of claim 1, wherein said per permanent magnets are arranged to produce substantially uniform magnetic flux density within said flow channel between said electrodes.
 3. The MHD pump assembly of claim 1, wherein said permanent magnets are arranged to have their magnetization vectors pointing in generally the same direction.
 4. The MHD pump assembly of claim 1, wherein said upper core structure and said lower core structure are made of material selected from the group consisting of iron, pure iron, Consumet core iron, mild steel, and Hyperco.
 5. The MHD pump assembly of claim 1, wherein said electrodes have curved surfaces facing the flow channel.
 6. The MHD pump assembly of claim 1, wherein said electrodes are made of material selected from the group consisting of tungsten, pure tungsten, tantalum, and molybdenum.
 7. A magnetohydrodynamic (MHD) pump assembly consisting an upper core assembly, a lower core assembly, and a flow channel; a) said flow channel being formed entirely by said upper core assembly and said lower core assembly; b) said upper core assembly comprising an upper core structure, permanent magnet, and electrically insulating material; c) said lower core assembly comprising a lower core structure, permanent magnet, two electrodes, and electrically insulating material; and d) said lower core assembly further comprising a groove forming in-part said flow channel.
 8. The MHD pump assembly of claim 7, wherein said per permanent magnets are arranged to produce substantially uniform magnetic flux density within said flow channel between said electrodes.
 9. The MHD pump assembly of claim 7, wherein said permanent magnets are arranged to have their magnetization vectors pointing in generally the same direction.
 10. The MHD pump assembly of claim 7, wherein said upper core structure and said lower core structure are made of material selected from the group consisting of iron, pure iron, Consumet core iron, mild steel, and Hyperco.
 11. The MHD pump assembly of claim 7, wherein said electrodes have curved surfaces facing the flow channel.
 12. The MHD pump assembly of claim 7, wherein said electrodes are made of material selected from the group consisting of tungsten, pure tungsten, tantalum, and molybdenum.
 13. A magnetohydrodynamic (MHD) pump assembly comprising an upper core assembly and a lower core assembly; a) said upper core assembly and said lower core assembly forming a flow channel suitable for flowing electrically conductive liquid; b) said upper core assembly comprising an upper core structure, permanent magnet, and electrically insulating material; c) said lower core assembly comprising a lower core structure, permanent magnet, two electrodes, and electrically insulating material; and d) said lower core assembly further comprising a groove forming in-part said flow channel.
 14. The MHD pump assembly of claim 13, wherein said per permanent magnets are arranged to produce substantially uniform magnetic flux density within said flow channel between said electrodes.
 15. The MHD pump assembly of claim 13, wherein said permanent magnets are arranged to have their magnetization vectors pointing in generally the same direction.
 16. The MHD pump assembly of claim 13, wherein said upper core structure and said lower core structure are made of material selected from the group consisting of iron, pure iron, Consumet core iron, mild steel, and Hyperco.
 17. The MHD pump assembly of claim 13, wherein said electrodes have curved surfaces facing the flow channel.
 18. The MHD pump assembly of claim 13, wherein said electrodes are made of material selected from the group consisting of tungsten, pure tungsten, tantalum, and molybdenum. 